JP5068084B2 - Polyamide multilayer film - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a polyamide multilayered film having both pinhole resistance caused by bending and pinhole resistance caused by repeated contact, and to provide its forming method. <P>SOLUTION: The polyamide multilayered film is constituted by laminating a polyamide layer (A) containing 80-100 wt.% of nylon-6 and 0-20 wt.% of a crystalline aromatic polyamide, a polyamide layer (B) containing 40-97 wt.% of nylon-6, 3-30 wt.% of a nylon-6/6, 6 copolymer and 0-30 wt.% of an aromatic polyamide and a barrier layer (C) containing a saponified ethylene/vinyl acetate copolymer in the order of A/B/C/B/A or B/A/C/A/B. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a polyamide-based multilayer film having improved pinhole resistance by bending and pinhole resistance by repeated contact.

  Conventionally, a multilayer film containing a nylon resin has been widely used in various directions as a film having gas barrier properties, toughness and the like. For example, a film composed of three layers of polyamide layer / barrier layer / polyamide layer is widely used for packaging.

  This multilayer film is used, for example, as a packaging film for foods distributed in the market. However, pinholes may be generated during transportation, transportation, etc., and the excellent gas barrier properties of the multilayer film are hindered by the pinholes. It was a result. Therefore, further improvement in toughness, especially improvement in pinhole resistance is desired from the market.

  The pinholes of this multilayer film include those that are caused by bending and those that are caused by wear due to repeated contact. In general, if the nylon resin layer is hard, pinholes due to repeated contact wear are difficult to form, but pinholes due to bending tend to occur. On the other hand, if the nylon resin layer is soft, pinholes due to bending are unlikely to occur, but pinholes are easily formed due to wear due to repeated contact. Therefore, a multilayer film having high pinhole resistance against both bending and repeated contact is strongly desired.

  In order to solve such a problem, the present applicant has reported that a polyamide film having a predetermined five-layer structure has excellent pinhole resistance due to bending and repeated contact (Patent Documents 1 and 2).

  However, the film of Patent Document 1 tends to be stretched easily by tension or heat during printing or laminating. Along with this, the deviation and variation from the regular pitch become large, and a problem occurs at the time of bag making in the subsequent process. Furthermore, there was room for further improvement in pinhole resistance due to repeated contact.

Moreover, although patent document 2 is excellent in pinhole resistance by bending, there is room for further improvement in pinhole resistance by repeated contact.
JP 2005-288923 A JP 2006-35511 A

  The present invention provides a polyamide-based multilayer film that has both pinhole resistance due to bending and pinhole resistance due to repeated contact, and a method for producing the same, with less film elongation due to tension and heat during printing and laminating. For the purpose.

  As a result of intensive studies to solve the above problems, the present inventor has found that a polyamide layer (A) containing 80 to 100% by weight of nylon-6 and 0 to 20% by weight of crystalline aromatic polyamide, nylon-6 Polyamide layer (B) comprising 40 to 97% by weight of nylon, 3 to 30% by weight of nylon-6 / 6,6 copolymer and 0 to 30% by weight of aromatic polyamide, and saponified ethylene-vinyl acetate copolymer It was found that a polyamide-based multilayer film in which a barrier layer (C) containing A is laminated in the order of A / B / C / B / A or B / A / C / A / B can solve the above problems . Based on this knowledge, further studies have been made and the present invention has been completed.

  That is, this invention provides the following polyamide-type multilayer film and its manufacturing method.

  Item 1. A polyamide layer (A) containing 80 to 100% by weight of nylon-6 and 0 to 20% by weight of crystalline aromatic polyamide, 40 to 97% by weight of nylon-6, 3 of a nylon-6 / 6,6 copolymer A polyamide layer (B) containing -30% by weight and 0-30% by weight of aromatic polyamide, and a barrier layer (C) containing a saponified ethylene-vinyl acetate copolymer are A / B / C / B / A, Or the polyamide-type multilayer film laminated | stacked in order of B / A / C / A / B.

  Item 2. Item 2. The polyamide-based multilayer film according to Item 1, wherein the aromatic polyamide contained in the polyamide layer (B) is a crystalline aromatic polyamide or an amorphous aromatic polyamide.

  Item 3. Item 3. The polyamide multilayer film according to Item 2, wherein the crystalline aromatic polyamide is polymetaxylene adipamide (MXD-nylon).

  Item 4. Item 4. The polyamide multilayer film according to Item 2 or 3, wherein the amorphous aromatic polyamide is a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid.

  Item 5. Item 5. The polyamide multilayer film according to any one of Items 1 to 4, wherein a copolymerization ratio of nylon-6,6 in the nylon-6 / 6,6 copolymer is 5 to 40 mol%.

  Item 6. Item 6. The polyamide multilayer film according to any one of Items 1 to 5, which is a multilayer film obtained by biaxial stretching 2.5 to 4.5 times in the MD direction and 2.5 to 5 times in the TD direction.

  Item 7. Item 7. The polyamide multilayer film according to any one of Items 1 to 6, wherein the polyamide multilayer film has a total thickness of 10 to 50 µm.

  Item 8. Item 8. The polyamide-based multilayer film according to any one of Items 1 to 7, further comprising a seal layer on one surface.

  Item 9. Item 9. A packaging obtained by bonding the both ends of the polyamide-based multilayer film according to any one of items 1 to 8 so as to form a cylindrical shape, and further bonding one end of the opening of the cylindrical material. bag.

  Item 10. Item 10. The packaging bag according to Item 9, which is for food packaging.

  Item 11. Resin composition for polyamide layer (A) containing 80 to 100% by weight of nylon-6 and 0 to 20% by weight of crystalline aromatic polyamide, 40 to 97% by weight of nylon-6, nylon-6 / 6,6 co-weight A resin composition for a polyamide layer (B) containing 3 to 30% by weight of an aromatic polyamide and 0 to 30% by weight of an aromatic polyamide, and a resin composition for a barrier layer (C) containing a saponified ethylene-vinyl acetate copolymer, A polyamide-based multilayer film characterized by being laminated by coextrusion so as to be in the order of A / B / C / B / A or B / A / C / A / B, stretched in two directions in the vertical and horizontal directions, and heat-treated. Manufacturing method.

  The polyamide-based multilayer film of the present invention has excellent pinhole resistance with softness that resists bending and hardness that resists abrasion due to repeated contact.

  The polyamide-based multilayer film of the present invention is excellent in processing suitability with little stretch of the film due to tension or heat during printing or laminating, and further excellent in stretchability, puncture strength, and impact strength.

  Therefore, it is suitable for the packaging of heavy goods, in particular, the packaging of foods such as rice cakes and winners. It is also suitable for packaging frozen foods that are transported at low temperatures.

Polyamide-based multilayer film The polyamide-based multilayer film of the present invention comprises a polyamide layer (A) containing 50 to 100% by weight of nylon-6 and 0 to 20% by weight of crystalline aromatic polyamide, and 40 to 97% by weight of nylon-6. A polyamide layer (B) containing 3 to 30% by weight of nylon-6 / 6,6 copolymer and 0 to 30% by weight of aromatic polyamide, and a barrier layer containing saponified ethylene-vinyl acetate copolymer (C Is a polyamide-based multilayer film laminated in the order of A / B / C / B / A or B / A / C / A / B.

  That is, both sides of the barrier layer (C) are sandwiched between two polyamide layers (B) having flexibility, that is, flexibility, and two polyamide layers (A) having hardness, that is, abrasion resistance. It has a laminated structure of at least 5 layers. Therefore, it has both hardness and flexibility, and has excellent pinhole resistance against bending and repeated contact. In addition, since the polyamide layer (A) contains a crystalline aromatic polyamide, there is a merit that it is excellent in processing suitability because there is little elongation of the film due to tension or heat.

  The polyamide layer (A) contains 80 to 100% by weight, preferably 85 to 100% by weight, more preferably 90 to 100% by weight of nylon-6 (polycapramide).

  The polyamide layer (A) contains 0 to 20% by weight of crystalline aromatic polyamide, preferably 0 to 15% by weight, more preferably 0 to 10% by weight. The crystalline aromatic polyamide is, for example, a polyamide composed of a diamine component containing an aromatic ring and a dicarboxylic acid component, and specifically, a xylylenediamine-based polyamide. Specific examples include polyamides composed of metaxylylenediamine and adipic acid, that is, polymetaxylylene adipamide (MXD-6 nylon).

  The polyamide layer (B) contains 40% to 97% by weight of nylon-6, preferably 55% to 97% by weight, and more preferably 65% to 95% by weight.

  The polyamide layer (B) contains 3 to 30% by weight of nylon-6 / 6,6 copolymer, preferably 3 to 25% by weight, more preferably 5 to 20% by weight. The copolymerization ratio of nylon-6,6 is 5-40 mol%, preferably 10-30 mol%.

  The polyamide layer (B) contains 0-30% by weight of aromatic polyamide, preferably 0-20% by weight, more preferably 0-15% by weight. As the aromatic polyamide, amorphous aromatic polyamide or crystalline aromatic polyamide can be used.

  As an amorphous aromatic polyamide, for example, a polymer whose main skeleton is polymerized from hexamethylenediamine and terephthalic acid and / or isophthalic acid can be mentioned. Specific examples include a polymer of hexamethylenediamine-isophthalic acid, a polymer of hexamethylenediamine-terephthalic acid, and a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid.

  The crystalline aromatic polyamide is, for example, a polyamide composed of a diamine component containing an aromatic ring and a dicarboxylic acid component, and specifically, a xylylenediamine-based polyamide. Specific examples include polyamides composed of metaxylylenediamine and adipic acid, that is, polymetaxylylene adipamide (MXD-6 nylon).

  The saponified ethylene-vinyl acetate copolymer constituting the barrier layer (C) is not particularly limited, but the ethylene content is 55 mol% or less, preferably 20 to 50 mol%, more preferably 26 to 44 mol%. The saponification degree of the vinyl acetate component is 90 mol% or more, preferably about 95 mol% or more.

  As a preferred embodiment of the multilayer film of the present invention, a polyamide layer (A) comprising 90 to 98% by weight of nylon-6 and 2 to 10% by weight of crystalline aromatic polyamide, 60 to 93% by weight of nylon-6, nylon A polyamide layer (B) comprising 5 to 25% by weight of a -6 / 6,6 copolymer and 2 to 15% by weight of an amorphous aromatic polyamide, and a barrier layer (C) comprising A / B / C / B And those laminated in the order of / A or B / A / C / A / B.

  As another preferred embodiment of the multilayer film of the present invention, a polyamide layer (A) comprising 90 to 98% by weight of nylon-6 and 2 to 10% by weight of crystalline aromatic polyamide, and 75 to 85% by weight of nylon-6. And a polyamide layer (B) composed of 15 to 25% by weight of nylon-6 / 6,6 copolymer, and a barrier layer (C) are A / B / C / B / A or B / A / C / A And those stacked in the order of / B.

  In addition, in each layer of the multilayer film of the present invention, different types of polymers may be mixed as long as the object of the present invention is not impaired, and an antioxidant, a heat stabilizer, a lubricant, an ultraviolet absorber, etc. It may be added to the extent that organic additives are usually added.

  The composition and blending amount of the two polyamide layers (A) and the two polyamide layers (B) may be the same or different from each other, but are the same from the standpoint of simplicity in the production of the multilayer film described later. Is preferred.

  The total thickness of the film of the present invention is 10 to 50 μm, preferably 10 to 30 μm. The total thickness of the polyamide layer (A) and the polyamide layer (B) is 3 to 49 μm, preferably 6 to 29 μm. Among them, the total thickness of the polyamide layer (A) is 1 to 47 μm, preferably 2 to 27 μm, and the total thickness of the polyamide layer (B) is 1 to 47 μm, preferably 2 to 27 μm. The thickness of the barrier layer (C) is 1 to 20 μm, preferably 1 to 15 μm.

  In addition, you may provide a sealant layer, an adhesive resin layer, etc. as needed between the outer layer or each interlayer of the multilayer film of this invention.

Manufacturing method The polyamide-based multilayer film of the present invention is obtained from T dice so that the resin composition of each layer is in the order of A / B / C / B / A or B / A / C / A / B described above A flat multilayer film can be obtained by coextrusion on a chill roll through which cooling water circulates.

  The obtained film may be uniaxially stretched or biaxially stretched (simultaneous biaxial stretching and sequential biaxial stretching). The stretching ratio is, for example, longitudinal stretching (MD) 2.5 to 4.5 times and lateral stretching (TD 2.5 to 5.0 times).

  For example, in the case of sequential biaxial stretching, longitudinal stretching is performed 2.5 to 4.5 times by a roll stretching machine at 50 to 80 ° C., and 2.5 to 5.0 times by a tenter stretching machine in an atmosphere at 80 to 140 ° C. And then heat-treated in the 180-220 ° C. atmosphere with the same tenter.

  The multilayer film obtained by subjecting the multilayer film of the present invention to uniaxial stretching or biaxial stretching (simultaneous biaxial stretching, sequential biaxial stretching) may be subjected to corona discharge treatment on both surfaces or one surface if necessary. You can also.

  The “pinhole resistance due to bending” of the multilayer film of the present invention is evaluated using a gelbo flex tester described in Examples described later. In the multilayer film of the present invention, the number of pinholes generated in the evaluation of the resistance to pinholes of 1,000 bends under the condition of 5 ° C. is 14 or less, preferably 8 or less, more preferably 6 or less. In addition, the number of pinholes generated in the evaluation of the resistance to pinholes with 1000 bends under the condition of 23 ° C. is 2 or less, preferably 0.

  The “pinhole resistance due to repeated contact” of the multilayer film of the present invention is evaluated by the method described in Examples below. Specifically, the multilayer film is mounted on a conical aluminum jig, and the apex of the conical shape is brought into contact with the cardboard through the multilayer film. Next, whether or not a pinhole was opened in units of 50 slides by placing a load of 63 g on the jig and sliding it at a speed of 2700 mm / min at a humidity of 65% within a moving distance of 45 mm. (For example, FIG. 1). The occurrence of pinholes is determined by dripping the penetrating solution where the top of the jig hits the film. Under such measurement conditions, in the multilayer film of the present invention, the number of sliding times until the pinhole is opened is 350 times or more, preferably 400 times or more, more preferably 450 times or more.

  Furthermore, the multilayer film of the present invention is excellent in stretchability, and hardly stretches and breaks. Moreover, the puncture strength (JIS Z-1707) is excellent at 8N or more, and further 9N or more. Moreover, the impact strength using an impact tester is excellent at 0.8 J or more, and further 0.85 J or more. Further, the thermal shrinkage rate is less than 1.6% in MD and less than 0.6% in TD, which is a small value.

  The multilayer film of the present invention is excellent in toughness, resistance to pinholes due to bending and repeated contact, and is therefore suitable for packaging heavy items, particularly foods such as bags and winners. It is also suitable for packaging frozen foods that are transported at low temperatures. Furthermore, since the multilayer film of the present invention has high transparency, it is easy to visually check the contents (food) when it is used as a food package.

  Hereinafter, the present invention will be described in more detail using Examples and Comparative Examples, but the present invention is not limited to these Examples.

  The raw material resins used in the following examples and comparative examples are shown below.

Nylon-6 (Ny6): 1022FDX04 (manufactured by Ube Industries)
Nylon-6 / 66 copolymer (Ny-6 / 66): 5034B (manufactured by Ube Industries): copolymerization ratio of nylon 66 of 20 mol%
Ethylene vinyl acetate copolymer saponification product: Nippon Synthetic Chemical Industry Co., Ltd .: DC3203FB (ethylene content 32 mol%, saponification degree 99.6%, MFR 3.2 g / 10 min (210 ° C., load 2160 g))
Amorphous aromatic polyamide (amorphous Ny): X-21 (Mitsubishi Engineering Plastics)
Crystalline aromatic polyamide (MXDNy): S-6011 (Mitsubishi Gas Chemical Co., Ltd.)

Example 1
Nylon-6 (100% by weight) was used as the resin composition for the polyamide layer (A).
Nylon-6 (80% by weight), nylon-6 / 66 copolymer (10% by weight) and amorphous Ny (10% by weight) were blended to obtain a resin composition for the polyamide layer (B).
The saponified ethylene-vinyl acetate copolymer was used as the resin composition for the barrier layer (C).

  The resin composition constituting each layer was coextruded on a chill roll in which cooling water circulates from a T die so as to be in the order of A / B / C / B / A to obtain a flat five-layer film. . This 5-layer film was longitudinally stretched 3.0 times by a roll stretching machine at 65 ° C., then stretched 4.0 times by a tenter stretching machine at 110 ° C. atmosphere, and further in an atmosphere at 210 ° C. by the same tenter. And a film having a thickness of 15 μm was obtained. The thickness of each layer was 3.5 / 3/2/3 / 3.5 (μm).

Example 2
Nylon-6 (95% by weight) and MXDNy (5% by weight) were blended to obtain a resin composition for the polyamide layer (A).

  Nylon-6 (80% by weight), nylon-6 / 66 copolymer (10% by weight) and amorphous Ny (10% by weight) were blended to obtain a resin composition for the polyamide layer (B).

  The saponified ethylene-vinyl acetate copolymer was used as the resin composition for the barrier layer (C).

  In the same manner as in Example 1, a 5-layer film of A / B / C / B / A with a thickness of 15 μm was obtained. The thickness of each layer was 3.5 / 3/2/3 / 3.5 (μm).

Examples 3-4
A composition and a composition shown in Table 1 were used, and a 5-layer film of A / B / C / B / A having a thickness of 15 μm was obtained in the same manner as in Example 1. The thickness of each layer was 3.5 / 3/2/3 / 3.5 (μm).

Example 5
A 5-layer film having a thickness of 15 μm was obtained in the same manner as in Example 1 except that the resin composition constituting each layer was in the order of B / A / C / A / B. The thickness of each layer was 3 / 3.5 / 2 / 3.5 / 3 (μm).

Comparative Examples 1-10
A 5-layer film having a thickness of 15 μm of A / B / C / B / A was obtained in the same manner as in Example 1 with the composition and formulation described in Table 2. The thickness of each layer was 3.5 / 3/2/3 / 3.5 (μm).

Test example 1 (characteristic evaluation results)
The following properties were evaluated for the five-layer films described in Examples 1 to 5 and Comparative Examples 1 to 11. The results are shown in Table 3.

[Extensible]
The number of stretching breaks in the 24-hour film formation was counted.
Number of break occurrences: 0 to 1 time ... ○, 2 times ... △, 3 times or more ... ×

[Abrasion resistance]
A film is attached to a jig made of aluminum with a cone shape using tape or the like, and the apex of the cone-shaped jig is placed on the cardboard through the film (for KOKUYO Campus, for fine puss, 430g / m ² ). The vertex R was set to a sliding direction R = 0.1 to 1.0 mm, and a direction R = 0.1 to 1.0 mm perpendicular to the sliding direction. Next, a load of 63 g was placed on the jig. Under a humidity of 65%, the jig is slid in parallel with the cardboard at a speed of 2700 mm / min and within a moving distance of 45 mm. The number of times was measured. For example, if it was opened at 300 times and not opened at 250 times, it was set at 300 times.

The occurrence of pinholes was determined based on whether or not the penetrating solution was dropped onto the film where the top of the jig had hit and permeated on white paper. The results are shown in Table 3.
400 times or more ... ○, 350 times ... △, 300 times or less ... ×
In addition, the schematic diagram of a measuring apparatus is shown in FIG. FIG. 2 shows an example of a conical aluminum jig.

[Puncture strength]
The puncture strength (N) was measured according to JIS Z-1707.
8N or more ... ○, 7N or more but less than 8N ・ ・ ・ △, less than 7N ・ ・ ・ ×

[Impact strength]
Impact strength (J) was measured using an impact tester (manufactured by Toyo Seiki Seisakusho).
0.8J or more ... ○, 0.7 or more but less than 0.8 ・ ・ ・ △, less than 0.7 ・ ・ ・ ×

[Flexibility]
The measurement was performed using a gelbo flex tester manufactured by RIKEN. A film formed into a cylindrical shape with a folding diameter of 150 mm and a length of 300 mm was attached to a gelbo flex tester, and a bending linear motion of 15.0 cm at a twist angle of 440 ° was repeated 1000 times at 5 ° C. and 23 ° C. Thereafter, the number of pinholes was examined using a penetrating solution. The number of pinholes was measured at a location of 300 cm ² in the center of the sample. The number of pinholes was measured for three samples, and the average value is shown in Table 3.
23 ° C (1,000 times): 0 to 2 ... ○, 3 to 4 ... △, 5 or more ... ×
5 ° C (1,000 times): 0 to 8 ... ○, 9-14 ... △, 15 or more ... ×

[Heat shrinkage]
A film sample of MD × TD = 100 mm × 100 mm was treated with boiling water for 30 seconds, and the shrinkage after the treatment was measured. It shows in Table 3 as an average value of four measurements.
MD: Less than 1.6% ... ○, 1.6% or more and less than 2.0% ・ ・ ・ △, 2.0% or more ・ ・ ・ ×
TD: Less than 0.6% ... ○, 0.6% or more but less than 1.2% ・ ・ ・ △, 1.2% or more ... ×

[Vertical pitch evaluation]
Cut the sample into strips that are long in the vertical direction (width: 20 mm), apply a load of 600 g under an atmosphere of 120 ° C, and evaluate the elongation between 40 mm marked lines in the center of the sample. Measurements were performed on five samples, and the average values are shown in Table 3.
Elongation: Less than 6mm ・ ・ ・ ○, 6mm or more and less than 7mm ・ ・ ・ △, 7mm or more ・ ・ ・ ×

  From Table 3, it turned out that the film of Examples 1-5 has the outstanding characteristic in any test. On the other hand, none of the films of Comparative Examples 1 to 10 could satisfy all the characteristics.

  In particular, the film of the example is notable in wear resistance and longitudinal pitch evaluation as compared with the films of Comparative Examples 7 and 8 corresponding to Examples 1 and 2 of Patent Document 1 (Japanese Patent Laid-Open No. 2005-288923). I found it excellent.

  Moreover, the film of an Example is remarkably excellent in abrasion resistance compared with the film of Comparative Example 9 and 10 corresponding to Example 1 and 2 of patent document 2 (Unexamined-Japanese-Patent No. 2006-35511). I understood.

The schematic diagram of the measuring apparatus used for evaluation of the pinhole which generate | occur | produces by repeated contact is shown. It is a figure which shows an example of a cone-shaped aluminum jig.

Claims (9)

A polyamide layer (A) containing 85 to 98 % by weight of nylon-6 and 2 to 15% by weight of crystalline aromatic polyamide, 60 to 93 % by weight of nylon-6, 3 of a nylon-6 / 6,6 copolymer A polyamide layer (B) containing -30% by weight and 2-15 % by weight of amorphous aromatic polyamide, and a barrier layer (C) containing a saponified ethylene-vinyl acetate copolymer are A / B / C / B Polyamide-based multilayer film laminated in the order of / A or B / A / C / A / B. The polyamide-based multilayer film according to claim 1 , wherein the amorphous aromatic polyamide is a copolymer of hexamethylenediamine-terephthalic acid-hexamethylenediamine-isophthalic acid. The polyamide based multilayer film according to claim 1 or 2 , wherein the nylon-6 / 6 copolymer has a copolymerization ratio of nylon-6,6 of 5 to 40 mol%. The polyamide-based multilayer film according to any one of claims 1 to 3 , which is a multilayer film obtained by biaxially stretching 2.5 to 4.5 times in the MD direction and 2.5 to 5 times in the TD direction. The polyamide multilayer film according to any one of claims 1 to 4 , wherein a total thickness of the polyamide multilayer film is 10 to 50 µm. Furthermore, the polyamide-type multilayer film in any one of Claims 1-5 which has a sealing layer in one surface. A packaging obtained by bonding both ends of the polyamide-based multilayer film according to any one of claims 1 to 6 so as to form a cylindrical shape, and further bonding one end of an opening of the cylindrical material. Bags. The packaging bag according to claim 7 , which is used for food packaging. Resin composition for polyamide layer (A) containing 85 to 98 % by weight of nylon-6 and 2 to 15% by weight of crystalline aromatic polyamide, 60 to 93 % by weight of nylon-6, both nylon-6 / 6 and 6 Resin composition for polyamide layer (B) containing 3 to 30% by weight of polymer and 2 to 15 % by weight of amorphous aromatic polyamide, and barrier layer (C) containing saponified ethylene-vinyl acetate copolymer The resin composition is laminated by coextrusion so as to be in the order of A / B / C / B / A or B / A / C / A / B, stretched biaxially and horizontally, and heat-treated. A method for producing a polyamide-based multilayer film.

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